Recent development in upconversion nanoparticles and their application in optogenetics:A review

Ion channels present in the plasma membrane are responsible for integration and propagation of electric signals,which transmit information in nerve cells.Malfunction of these ion channels leads to many neurological diseases.Recently,optogenetic technology has gained a lot of attention for the manipulation of neuronal circuits.Optogenetics is a neuromodulation approach that has been developed to control neuronal functions and activities using light.The lanthanide-doped upconversion nanoparticles(UCNPs)absorb low energy photons in near-infrared(NIR) window and emit high energy photons in the visible spectrum region via nonlinear processes.In the last few decades,UCNPs have gained great attention in various bio-medical applications such as bio-imaging,drug delivery and optogenetics.The near-infrared illumination is considered more suitable for optogenetics application,due to its lower degree of light attenuation and higher tissue penetration compared to visible light.Therefore,UCNPs have been considered as the new promising candidates for optogenetics applications.Upconversion nanoparticlemediated optogenetic systems provide a great opportunity to manipulate the ion channel in deep tissue.Herein,we summarize the upconversion photoluminescence in lanthanide doped nanomaterials and its mechanisms and several approaches adopted to tune emission color or enhance upconversion efficiency.Recent advances of lanthanide-doped UCNPs design strategy and their mechanism are reviewed.Then,we discuss the neural circuitry modulation using upconversion nanoparticles mediated optogenetics.Moreover,the future perspectives towards optogenetics are also included.

Antibacterial Behaviour of Quaternized Poly(vinyl chloride)-g-Poly(4-vinyl pyridine) Graft Copolymers

Amphiphilic graft copolymers consisting of poly（vinyl chloride）（PVC） main chains and poly（4-vinyl pyridine）（P4VP） side chains were synthesized via atom transfer radical polymerization（ATRP） using direct initiation of chlorine atoms. The successful synthesis of PVC-g-P4 VP graft copolymers was confirmed by Fourier transform infrared spectroscopy（FTIR） and proton nuclear magnetic resonance（1H-NMR）. Transmission electron microscope（TEM） and small angle X-ray scattering（SAXS） analysis showed that PVC-g-P4 VP exhibited microphase-separated, ordered structure with 37.6 nm of domain spacing, which was not observed in neat PVC. For antibacterial applications, the tertiary nitrogen atoms of PVC-gP4 VP was quaternized using 1-bromohexane, as confirmed by FTIR measurements. Bacteria including Escherichia coli（E. coli）, Staphylococcus aureus（S. aureus）, Bacillus cereus（B. cereus）, and Pseudomonas aeruginosa（P. aeruginosa） were completely killed in 24 h on the quaternized PVC-g-P4VP（46% grafting） surface, indicating its excellent antibacterial behavior while it showed to be cytotoxic to mammalian cell.